The Effect of Health Insurance on Utilization and Outcomes: The Oregon Lottery. Understanding the consequences of health insurance coverage is central to evaluating proposals to expand or modify health insurance coverage in the U.S. It also has important long-run fiscal implications for Medicare. Yet there is remarkably little convincing evidence on the effect of insuring the uninsured on health care utilization, health outcomes, and overall well-being, because it is difficult to disentangle the effects of health insurance from other factors that differ between the insured and uninsured that also affect health. A remarkable opportunity has presented itself for providing just such evidence. For a limited window in early 2008, Oregon opened a waiting list for enrollment in its previously closed public health insurance program for certain low income adults, and then randomly drew names from the list to determine who would be given the opportunity to enroll. This unique policy environment provides researchers with a rare occasion to bring the strengths of random assignment - the standard in medical trials - to address a critical social policy question. We have already begun surveying those selected and not selected in the lottery, and propose to use NIA funding to greatly extend the reach of our data collection and analysis, including over-sampling of the near-elderly (those aged 50-64) whose health risks are in many ways similar to those aged 65 and up and who will soon age onto Medicare themselves. We propose to capitalize on this extraordinary and unique opportunity to address questions in three different areas: First, how does insurance affect health care utilization? Second, what are the effects of insurance on health? Third, how do the effects of health insurance differ for different groups? We will answer these questions by drawing on three data sources: semi-annual mail surveys, an in-person data collection effort including measurement of physiological markers of health, and administrative records on hospital and emergency department use. PUBLIC HEALTH RELEVANCE: Understanding the consequences of gaining access to health insurance is central to evaluating proposals to expand or modify health insurance coverage in the U.S. The proposed research will take advantage of a unique health insurance lottery currently underway in Oregon to evaluate the causal effects of insurance on health care utilization and health outcomes. The project will powerfully leverage existing resources to allow us to explore the effects of insurance expansions for those groups of particular policy importance.